Forget the star soprano of the moment. At the Metropolitan Opera, the reigning divas are three sheep.

The animals make a memorable appearance in Thomas Adès' The Exterminating Angel, a contemporary opera that received its North American premiere at the Met last week. The work, based on the film by Luis Buñuel about a group of elite partygoers trapped inside a home, has been praised as a work of surreal genius.

The sheep, seen on stage as the audience enters the theater, are key to the opera's strange, unsettling nature. At the onset, it is unclear why the animals are there - and as the work progresses, they figure into the plot in only a small way. But their mere presence almost ensures this isn't your typical night at the opera.